"A: For ten years we have used the same name - "OpenOffice.org" - for both the Community and the software. We've decided it removes ambiguity to have a different name for the two, so the Community is now "The Document Foundation", and the software "LibreOffice". Note: there are other examples of this usage in the free software community - e.g. the Mozilla Foundation with the Firefox browser."
The Document Foundation LibreOffice Productivity Suite

I read an article about it recently, and it seems it's not a whole lot different from OpenOffice yet. I don't know though, I am yet to test it. I've got Office 2007 Ultimate though and I rather use that.

LibreOffice is the "new" OpenOffice, when Sun Oracle bought OpenOffice (a couple of months back IIRC), a complete copy of all the OpenOffice code was maintained open-source, and thats what LibreOffice is, since the original developers of OpenOffice didn't knew what Sun was/is going to make with OpenOffice from then on.